1. Field of the Invention
The present invention relates to a motorcycle power unit including: an internal combustion engine having an oil pan connected to a lower portion of a crank case that rotatably supports a crank shaft and a continuously variable transmission that continuously varies rotational power of the crank shaft to transmit the resultant rotational power to a rear wheel. In the motorcycle power unit, a crank chamber that contains the major part of the crank shaft is formed in the crank case, while a continuously variable transmission chamber that contains the continuously variable transmission is formed of the crank case and of a cover member connected to the crankcase.
2. Description of Background Art
In Japanese Patent Application Laid-Open Publication No. Hei 10-238327, a motorcycle power unit is disclosed that includes an internal combustion engine and a gear transmission that varies an output of the internal combustion engine to transmit the output to a rear wheel. In the motorcycle power unit, an oil pan, which reserves lubrication oil to be supplied to each lubrication portion of the internal combustion engine and the gear transmission, is connected to a crank case.
In addition, in Japanese Patent Application Laid-Open Publication No. 2002-357265 a motorcycle power unit is known wherein an oil pan, which reserves oil for lubrication of a continuously variable transmission and for speed control thereof, is connected to a crank case that contains the continuously variable transmission.
As disclosed in Japanese Patent Application Laid-Open Publication No. Hei 10-238327, in a case of sharing oil for use in the lubrication portion of the internal combustion engine with oil for use in the transmission side, one kind of oil may be sufficient. However, depending on the kind of transmission, there is a case in which a kind of oil different from that used in the lubrication portion of the internal combustion engine should be used in the transmission side in order to make full use of a characteristic of the transmission.
In view of the above point, Japanese Patent Application Laid-Open Publication No. 2002-357265 discloses the use of an oil pan dedicated to the transmission. However, if this technique is simply applied to a motorcycle, an oil pan for the internal combustion engine side and a other oil pan for the continuously variable transmission side are needed. Concurrently, parts for connecting each of both oil pans to the crank case are required. As a result, an increase occurs in the number of parts. Moreover, special ideas are required for the shape of the oil pan, in the case of ensuring a different amount of oil for each of the internal combustion engine side and the continuously variable transmission side in the motorcycle with the limited space.